It requires only approximately 12 horsepower to maintain an automobile the size of a Volkswagon "BEETLE" moving at a constant speed of approximately 55 m.p.h. Of course, greater power is required to accelerate an automobile from a standing position to its cruising speed. However, the average automobile must have an engine of considerably greater power than is required to maintain it at its normal cruising speed. This is because an internal combustion engine has relatively low torque at low speeds. Thus, the internal combustion engine in an automobile must be made relatively powerful to provide acceptable acceleration.
In contrast, a direct current electric motor develops its greatest torque at low speeds. Therefore, a combined hybrid power plant for an automobile having a relatively small internal combustion engine (for example, approximately 20 horsepower for a small automobile) combined with a direct current electric motor will provide a relatively uniform torque over the speed ranges of the internal combustion engine and electric motor. Internal combustion-electric motor hybrid power plants for automobiles have been proposed in the past but apparently have met only limited success.
It has also been known in the prior art that a major portion of the energy developed by the burning of fuel in an internal combustion engine is lost as heat through exhaust and cooling. As a matter of fact, more energy is lost in this manner than is delivered as usable energy to the crank shaft. For example, it is believed that approximately 2.8 times as much energy is lost through exhaust and cooling as is delivered to the engine crank shaft. The foregoing would indicate that an internal combustion engine having approximately 20 horsepower output to the crank shaft loses approximately 56 horsepower in heat through exhaust and cooling. If approximately one-third of this energy loss could be recaptured, the efficiency of the internal combustion engine would be doubled. In other words, the fuel consumption for a given power output would be cut in half.